First‐Principles Study of Structural, Mechanical, Electronic, Thermodynamical, and Optical Properties of XGaO ₂ (X = Rb and Cs): Unlocking Its Green Energy Potential

Lead‐free metal oxides are currently considered promising options for green energy harvesting, particularly as active semiconductors in photocatalysts, to meet future‐generation energy demands. This research conducted a first‐principles investigation into XGaO 2 (X = Rb and Cs) metal oxides. Density functional theory (DFT) simulations were employed to evaluate the structural, mechanical, electrical, optical, and thermodynamic characteristics of XGaO 2 . The material XGaO 2 exhibits ductile behavior in nature as well as an anisotropic character. The studied materials exhibit stable structures with direct bandgaps of 2.39 and 2.67 eV for RbGaO 2 and CsGaO 2 . Various optical parameters were predicted. The high optical conductivity and reflectivity, and the better dielectric constant of CsGaO 2 , indicate that this material could be a potential candidate for optoelectronic device fabrication. The thermal effects on heat capacity, entropy, enthalpy, and free energy were analyzed. The band edges of RbGaO 2 and CsGaO 2 showed that the materials have the precise oxidation and reduction potentials to break down contaminants in wastewater and generate hydrogen through water splitting. Thus, the findings of this research could be helpful to get more suitable devices for solar‐driven H 2 generation via water splitting and dye degradation from wastewater.